The preparation of sintered NdFeB magnet with high-coercivity and high temperature-stability

The NdFeB magnets with high intrinsic coercivity have been produced by using the conventional powder metallurgy method (including SC, HD and JM) of sintered NdFeB magnets. The effects of grain boundary phases on the microstructure and magnetic properties of as-sintered and annealed magnets have been tried to investigate. Also the Curie temperature of the magnets was studied. By adopting suitable component ratio of some heavy rare-earth atoms and some micro-quantity additives, we have prepared high-coercivity sintered NdFeB magnets with magnetic properties of _jH_c=36.3kOe, B_r=11.7kGs and (BH)_max=34.0MGOe. The temperature coefficient of residual magnetic flux of the magnets (between 20 and 200°C) is -0.113%/°C, while the temperature coefficient of intrinsic coercivity -0.355%/°C. The Curie temperature of the magnets is about 342°C.